Field of Invention
The present invention relates to a memory. In particular, the present invention relates to one-time programming and repeatedly random read integrated circuit memory.
Description of Related Art
One time programming (OTP) memory and multi time programming (MTP) memory have three main kinds as shown below. The first kind memory is a traditional kind memory that metal atomic in the metal connection will be moved due to electromigration when there is a high current, thereby the metal connection is disconnected so as to form fuse-type wire memory. It can be implemented by Al/Cu/Silicide liner, poly-Si liner, contact via, or metal gate liner.
The second kind memory is that as the thickness of the gate dielectric layer is getting thinner, the breakdown electric field of the dielectric layer becomes lower; and therefore, such breakdown causes the changes of gate dielectric conductivity from low to high so as to form anti-fused type. Compared with metal electro-migration fused breakdown, anti-fused breakdown of the gate dielectric layer is steady in operation and needs lower area per unit cell. Hence, the anti-fused type memory becomes more popular in OTP application.
The third kind memory is using charge storage. For example, silicon-oxide-nitride-oxide-silicon (SONOS) structure or floating-gate on a MOSFET forms as a flash memory; or using spacers of the poly-Si CMOS stores electric charge for achieving information storage.
The first kind memory needs large area, high operation current, and its read margin is small. Therefore, the first kind memory is merely suitable for simple code programming. The second kind memory has better retention and does not need additional photomask. Furthermore, the second kind memory does not need special manufacturing process; and therefore its manufacturing cost is low. However, its drawback is charge loss and yields to poor retention.
In view of the foregoing, problems and disadvantages are associated with existing products that require further improvement. However, those skilled in the art have yet to find a solution.